'03 YZ450F: Hard to Kick Over. Decompression Problem?

3 replies to this topic
  • bgates

Posted December 16, 2006 - 09:03 AM


I just picked up an '03 YZ450f and it is a biatch to kick. To kick it through top dead center I almost have to lift my foot up and beat down on it. Or if I press my foot on it and giggle it for a while, it pushes through. This is my first experience with an auto decompression (used to the 426 manuel lever). Could this be a problem with the auto decompression? Or does it sound like a valve problem?:thumbsup:

  • grayracer513

Posted December 16, 2006 - 09:15 AM


One of the mistakes people new to auto decompression, but experienced with manual decompression sometimes make is in thinking that they need to push the engine past TDC to start it. You don't; that's the point of the system. It does not actually release all compression, it reduces it from 12.5:1 to more like 7 or 8:1, originally so that an electric motor could turn the engine without weighing at least as much. If your rings are in good shape, it should still be difficult to push it over the top.

But if you either push it up against compression, reset the kick starter, and drive it through, or simply don't worry about where it is and just kick it as if it were a two-stroke, it will crank through.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • bgates

Posted December 18, 2006 - 04:42 PM


Well, I took my new bike to Ocotillo yesterday and when I was kicking it over, the crankcase cracked open right at the kickstarter. Both sides! I about flipped. I had a feeling that it was unusually hard to kick over. I guess being kicked so hard for who knows how long (the guy who sold it to me probably knows how long) it finally just gave away.:thumbsup:

What are thoughts on welding a cracked crankcase? What are my options? I'd like to spend less than $1000. I obviously also need to find out what caused it to be pain to kick over.

  • bob426

Posted December 21, 2006 - 11:35 AM


Whattup B-gizzle.. Man O man I feel your pain :devil: :thumbsup:

Anyway, no info yet.. workin on it though. I would post this in a new thread, and also search the forums for similar problems. Hope to get you back out there asap:ride:

Related Content


Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.